aikman



B. s. AIKMA N CONTROL SYSTEM FOR CQMPRESSORS AND THE LIKE '7 Sheets-Sheet 1 Original Filed May 21, 1917 32 a7 10 3O 34 a5 2 Ll ll 3:

4 z 6 t 2 3 3 2 2. y n a o o 2. 210 9 5 M 1 3 s 8 t w 4 u W @n 1 I? l 0 3 \rflw 4 April 7, 1925.

B. S. AIKMAN CONTROL SYSTEM FOR COMPRESSORS Ail!) THE LIE 7 Shee'ts-Sheet 6 Original. Filed Kay 21, 1917 1 lI/lIa/Illllli v j? elgfbz Reisaued Apr.-7, 1925.

j uu rrsn- STATES; PATENT; OFF-ICE.

BURTON S. AIRMAN, OF WHITEFISH BAY, WISCONSIN, ASSIGNOR TO NATIONAL BRAKE & ELECTRIC COMPANY, OF MILWAUKEE, WISCONSIN, CORPORATION OF WISCON SIN.

CONTROL SYSTEK FOR COMPRESSORS- AND THE LIKE.

Original N0. 1, 400,1B3, dated December 13, 1921, Serial No. 169,997, filed Kay 21, 1917.- Applicatio i reissue-filed Decemberv 10, 1923. Serial No. 679,810.

To all whom it may concern:

Be it known that I, VBURTON S. AIKMAN', a citizen of the United. States, residing at the village of WhitefishBay, in the county of Milwaukee and State of Wisconsin,"have invented a certain new and useful Improve ment in Control Systems for Compressors and the like, of which the following is' a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specificas tion.

My invention relates to asystem'of 'con trol for air-compressors and the like.

Due to the simplicity, safety and adaptability ofcompriassed air it has.come into very eneral use. It is particularly desirable ioroperatingwcertain types of intermittently active apparatus which of necessity must be isolated and subject to infrequent attention or inspection.

Railway switching and interlocking plants,

pumping-plants and the like are instances of ."such installations. I

The reliabilityof compressed air as an operating medium recommends it for some types of installation. To keep the over-all reliability of the plant at a maximum it .is necessary to safe-guard the compressor and particularly the electric motor and other electrical equipment. It is better to prevent the motor and compressor from being start ed than to allow the same tostart and to be'damaged. The plant can .be operated for a time on the air in the main reservoir even at reduced pressure while attention-is given to the motor and the condition or obstruction removed.

11y invention aims primarily to provide a starting and control system for motor driven compressors which. controls automatic stopping andstarting of the motor and loading and unloading of the compressor and which is particularly characterized by provision for safe-guarding the electrical apparatus as well as the compressor itself against damage.

There are two pieces of electrical apparatus which .are to be protected namely the motor and the starting resistance. j- -Auto-'= matic electrical protection "of-*- thesepieces' would entailexpensive :apparatus too complicated and delicate forthe attendants "tooperate or.. ii-riderstand and which would not give as" -gre'at a degree of protection'as the device of my invention. I In carrying out the'above'I em'ploya main" switch for connecting the motor primary circuit to the power main; with .a suitable. starting resistance in circuit either in the primary orsecondary of the motor. "This main switch is governed by anoperating element which holds'the switch closed for a predetermined time to start the"moto'r.' If

some condition exists which would prevent the motor from starting and picking up speed such for instance as an open phase on a polyphase circuit, excessive mechanical friction, improper voltage or frequency, excessive 1oad open secondary,'or any'of the things which might occur, and; the motor does not come up to. speed in a predeter" mined timethe main switch automatically" opens. This is necessary because the start operation and if it is .left in' the circuit too ing resistance is not designed for continuous long itwill be overheated and damaged.

I provide a cut-out switch for the --sta'rt ing resistance and an operating element/for the switch which depends upon the motor coming up to speed. For this purpose I. employ a hydraulic system having a gradu ated orifice governing the escape of the liq- I uid from the system at a predetermined rate" and a pump operated in unison with the motor shaft for pumping liquid into the system in accordance with the speed of the motor. If themotor speeds up properly and exceeds a certain critical speed pressure ac- '90 Operation of the c'umulates in the hydraulic system and operates the cut-out switch. cut-out switch locks the main switch in closed position. Further accumulation of pressure by the motor coming up to full speed operates a pressure controlled element that loads the compressor.

This hydraulic system becomes the controllingmeans for the motor and the comopened so more flexible and reliable than a system of.

tiate another starting .and' loadingbf thecompr'essorfor replenishing the air supply as above outlined.

Suitable apparatus may opening the hydraulic system currence of any electrical or mec be employed for upon them:- anical conditions that may be dangerous or undesirable.

This provides a control system which is fuses overload switch orthe like, although m invention may be applied in conjunction w1th' them. The device is a self contained plant complete in itself and not requiring a switch-board to be set up and connected up as would be necessary for mounting electrically controlled safety devices.

i In developing the main idea above outlined I have found it necessary to produce a number of improvements in various parts of an automatic pumping plant or system and hence my invention has other more specific objects. g As an example of such further object it is the aim of my invention to put the 'pump and the starter system under the control of the lubricating system. A. further aim of the invention is to provide improvedmeans for controlling the system for cooling the com ressor. Another aim is the provision 0 an improved blow-out for the main switch. A further aim is the provision of over-load control means for the system. Numerous aims and objects'will be apparent from the following specification. 3

In the accompanying drawings which form apart of the present specification I have illustrated one embodiment in which my invention may appear.

Figure 1 is a side elevation of a compressorand the operating and control mechanism therefor;

Fig. 2 1s a rear end elevation of thesame;

Fig. 3 is a bottom 'planview of the switch board showing the main switch starting resistance switch and starting resistances;

Figs. 4, 5, 6, and 7 are parts of a comprehensive diagram showing diagrammatically the connection and operative-relation of the various parts. (Figs. 4, 5 and 6 are to be laid beside each other from left to right and Fig 7 is to be laid below Fig. 4.)

ig. 4 shows in elevation the main switch an operating medium,

and the starting resistance switch with the elements for operating the same; i

Fig. 5 shows the pressure governor, the' coolin water control and the suction valve contro Fi 6 shows the operating element for disab ing the suction valve;

Fig. 7 shows the pump and connections in the motor base;

Fig.8 is a view similar to Fig. 5, showing the governor in running 'tion;

v Fig. 9 is a section of the valve unloading cylinder when the same is in the starting position; 7

Fig. 10 is a view of the same in running position;

' Fig. 11 isa right side elevation partly in section of the main switch;

Fig. 12 is a left side elevation partly in section of the startin resistance switch;

Fig. 13 is a rear e evation of the switch board showing the motor starting resists ances and the connections;

Fig. 14 is a diagram of the electric circuit employing an overload protective device for unloading the compressor when the load upon the motor is excessive; and

Fig. 15 is a diagram of the circuit connections without said protective device.

Fig. 16, is a diagram of a modified form of pressure controlling means; and

Fig. 17 is a-plan view of the governor employed in the modification.

In carrying ont my invention I have made use of the following general instrumens talities. j

I employ a pressure controlled governor subject to the air pressure for initiating the necessary starting and stopping actions for cutting in'and out the action of the driving motor and for initiating the steps of loading and unloading the compressor. A

I employa hydraulic pressure system for operating a switch which brings the motor up to speed, for loading the compressor and for controlling the flow of cooling water to the compressor jacket. This hydraulic system employs the oil used for lubrication as thus further safeguarding the'mechanism.

I provide further an overload electrical relay governing the hydraulic system. Thus I provide asystemin which loading of the compressor will not occur if any disarrange-' ment of the electrical mechanism of the compressor or of the lubricating system should occur or if low line or overload on' the motor should occur.

The compressor 1 and motor 2 are mounted u' n a common base This base provides a pedestal 4 for the motor 2. The motor has a driving shaft 5 bearing a pinion 6 meshing with the gear 7 which gear is mounted on the end of the crank shaft-8 of the compresor.

The base 3 supports a housing or crank casvoltage or frequency on the ing 9 for inclosing the crank shaft and the gears and this housing is made tight to provide a suitable bath of oil for lubricating the ings, the pistons and cylinders and other bearings. Each side of thecrank casing/is accessible through the removable plate s10 and 11 and'a removable plate 12 at the front or controller end permits access to the oil 10 pump of the hydraulic system' later to be described.

The motor 2 is of the wound rotor type. The primary leads 13 ass from the motor through a suitable con uit which enters the base 3 at the rear as is shown at 15 and emerges from the front of the base as shown 'at 16 where the leads are connected to the necessary feed wires through the main circuit controlling switch 17. The secondary 0 leads 18 which connect with the rotor pass in througli a suitable conduit entering the rear of the base at 20 and emergingfrom the front of the base at 21 from whence these leads emerge and are connected to the starting resistances 22, 23 and 24 which are .mounted upon the back of the switch board 25. This switch board is mounted upon the .compressor base 9 at the front of the same in a vertical position. A suitable short circuiting switch 26 for short-circuiting the. secondary resistances. is mounted upon the front of the switch-board 25 close to the main circuit controlling switch 17.

Each compressor cylinder is provided with \one'or more suction valves 27 that are normally held closed by means of springs 28 except when they are open during the suction stroke. The spring 28 engages the upper end of the stem 29 and, tends to hold the valve 27 against its seat. Above the stem 29 and preferably axially in line with the same is provided a thrust rod or unloading rod 30 for 'each valve. The rod 30 passes through a bushing 31 which is mounted in the upper part of the hollow cylinder head 32 and is normally held in raised position by means of V the spring 33 while the compressor is in the operating condition. A shaft 34 is pivoted slightly above the compressor cylinder and upon this shaft are clamped operating arms 35 bearing adjustable spring plungers 36 in a casing 37 at the outer end of the same for holding the suction valve 27 open for unloading the compressor. Each of the operating arms 35 by means of its yielding spring plunger 36 is able to unload the cooperating valve at the time that that valve is drawn down by the suction stroke of the corresponding piston. This is fully described in 69 the co-pending application of W. I. Riel.

V ards, Serial Number 804,958, now Patent Number 1,230,925. A single unloading arm 38 is connected to the unloading shaft 34 and serves to operate simultaneously all of the arms 35.

connected to the end of the shaft 8. A small the rear ofthe compressor is mounted a valve 39 controlling the admission of cooling water from the water inlet 40. to the gears, the crank-shaft and crank-pin, bean/jacket of the compressor cylinders. 1

connected to the end of the shaft-8 I-have provided a small oil pump 47 which has an eccentric 48 well 49 is formed near'the end of the crank" v case and the pump-47 is lowered into the same'and held upon the base 3 by means of suitable lugs 50 on the frame of the pump 47. As above explained the crank case contains a bath of oil and this oil flows into the well 49 through an opening 51. The'oil is introduced through a'pipe 52 the upper end of which is covered by the screw cap .53. A gage glass 54 is connected by means of a short piece of pipe and a T 56 to the pipe 52 so that the gage glass 54 is in communication with the oil in the crank case. To fill the case the cap is unscrewed and oil is poured into the pipe 52 until the level of the same is brought to substantially the top of the pipe 52 as is shown by the dotted line 57. When the compressor is running the oil level drops tosubstantially the line 58 inasmuch as some of the oil is taken up by the pumpand is distributed throughout the system, as will be explained later, and in view of the fact that some of the oil. is splashed up and is running down-the side walls and the like. The'line 59 represents the danger level when the oil drops below the intake 60 of the pump 47.

Having now designated the main pieces or groups of apparatus 1 shall proceed to a detailed description of the various pieces of apparatus or groups of elements starting with the hydraulic oil system for-operating the unloader and the starting resistance.

switch. 4

llg/rira'ulic system for operating the loader and starting resistance switch.

I The pump 47 has a suitable operating pis the valve is opened but not so great as tograduated discharge orifice 68 which ori ce is adjustable to vary :the rate of dischar .therethrough ;is connected in the zhlydaullc mai'n 66sat any convenient point where the' discharge from the orifice will flow back into the'crank-case. The pipe 69 connected toan opening in the wall 70 of the crank case housing5- communicates through .a separable fitting 71 to the hydraulic inlet port 72 of the switch operating cylinder :73 for the starting resistance switch 26. The cylinder 73' is removabl-y mounted upon the face of the switch-board 25. The upper end of the cylinder 73 isprovided with a housing 74 through the upper end of which the piston rod. 75- projects and within which is inclosed a spring 76 which tends :to move the piston 77 tothe lowermost osition as is shown in Fig. 12. When the p unger 75 is raised to its uppermost position, it short-circuits the starting resistances 22, 23 and'24 in a manner which will be described in detail later. Suflice it to say thatthe movable contacts 78 and 79 will be closed against the stationary contacts 80 and 81,. thus placin the motor 2 directly across the power leads or full speed, full load operation. The cylinder 73 is provided with a. separable head; 82 hearing a relief vaive'83 which normallycloses a port 84 of suflicient size and capaclty to relieve the pressure of oil within the cylinder when drain the cylinder at once. The valve 83 has a stem '85 which is connected to a plunger 86' -restingupon a flexible diaphragm 87 which is held in place-by a recessed plug 88, the rea pipe 90 that connects the recess or chamber to the auxiliary air reservoir 42 A spring 91 normally holds-the valve 83'upon its seat so that oil pumped into the. cylinder 73 tends to raise the piston 77. The chamber 92 which is -formed below the valve 83 and above the diaphragm 87 is connected by a separable pipe'93 to an o ening 94 in the top of the crank case 9. T us 011 that is discharged through the valve port 84 is returned to the interior of the crank case. The piston 77 whenit is at the top of its stroke rests against a shoulder formedat the upper end of the cylinder bore so that the pressure of the fluid upon the piston 77 is mainly taken up at. this point anddoes-not injure the contacts 201 and 244. Any of the oil which leaks past the piston 77 passes out the overflow 330 through the passage 329 and back'to'the crank case. This passageway at the same time permits of rapid return of the piston 77 since some of the oil in passing out of the exhaust port 84 will be projected through the passageway 329 and overflow 330911101: into-the cylinder on top of the piston mom The hydraulic 66 is connected by a pipe 95 :to athe unloadingx cylinder 96 :Eor unloading the valves pf It e compressor. The

cylinder 96 .is in fact a compound cylinder comprising the main ibore 97 within which plays-the piston 98, 'flthlS piston being connectcd=bya stem-99 to a piston rod :100. The

upper en'd of. the piston rod 100 passes through the end of the-operating arm 38 as r is shown at 101 having a collar 102 adapted to bear upon the end 101. The upper end of the cylinder 96 is covered by a housing 103 which ineloses a relatively stifi spring port 105 communicates by means of a passage 106 with an opening 107 in the top of the crank chamber 108 upon which the cylinder 96 is-mounted. The lower end of the cylinder 96 projects down into the crank case and is closed off by the cylinder "head 109 which contains a valve port 110 normally closed by a valve 111. The cylinder 96 is provided with a liner or auxiliary cylinder 1'12'mounted upon theinside of the head 109 axially in line with the bore 97.

The cylinder 96 is counterbored as is shown at 113 to provide apassageway around the cess or chamber 89 of which lsconnected to outside of the auxiliary cylinder 112, this passageway 113 being in communication with the pipe 95 and communicating with the interior of ,the auxiliary cylinder 112 through three sets of ports, namely the ports 114 adjacent the cylinder head 109 at the lower end of the auxiliary cylinder 112, the ports 115 at the opposite end of the cylinder 112. and the intermediate ports 1 16.

The auxiliary cylinder 112 is provided with two pistons 117 and 118, slidable within the bore of the cylinder. The valve 111 has astem 119 which is connected to the lower piston 118. A spring 120 surrounds 'the valve stem 119 and tends to force the piston 117 is closed oil by the projecting stem 124 secured to the piston 98 that moves in the main bore 97 when the mechanism is,

operating and the compressor loading cylinders 73 and 96 respectively'. v,

A certain relation exists between the starting switch operating cylinder and the unloader operating cylinder which is essential to the proper operation of the device and for the purpose of bringing out this relation I shall now describe the operation of this much of the machine.

. loader mechanism.

The proportion of the spring strength for the switch operating cylinder with respect to the spring strength of the unloading mechanism operating cylinder 96 'is such that for the same oil pressure in both of these cylinders, the spring 76 will. be compressed before'the spring 104 is-oompressed. That is to say the oil pressure which will be sufficient to move the piston 77 against the spring 76 will be insufficient to move the piston 98 against the spring 104. As oil is forced into the main 66 by operation of the pump 47 and as the speed of the driving motor increases the oil pressure in the main 66 and connected conduits will rise until such a pressure is obtained where the piston 77 begins to move upward and finally this piston is moved upward to such an extent that the switch contacts 78 and 79 will be brought against the stationary contacts 80 and 81 and the starting resistance cut out of the circuit. It can be seen that a predetermined speed is necessary before the short circuiting switch will be operated because of the escapement of pressure through the graduated orifice '68. As the speed of the motor increases after cutting out the starting resistance the pressure will rise higher.

in the system and at full speed will reach a pressure sufiicient to move the piston 98 against the spring 104. As previously explained the spring 104 normally holds the operating arm 38 of the unloading device in its lower position so that the suction valve 27 is held 011' of its seat. The oil under pressure enters through the pipe 95 into the counterbore 113 and from there passes through the upper port 115 to the interior of the auxiliary cylinder 112 forcing the piston 98 upward. As the piston 98 rises the proiecting stem 124 uncovers the port 123 in he top of the upper auxiliary piston 117 filling the space between the two auxiliary pistons 117 and 118 with oil thusegualizing the fluid pressure upon both sides 0 the piston 117. At the same time oil enters the bottom of the auxiliary cylinder through the lower ports 114 thereby equalizing the pressures upon both sides of the lower auxiliary piston 118 and hence the springs 120 and 122 of the two auxiliary pistons are free to operate, the'first mentioned spring 120 serving to keep the valve-lll closed and the second spring 122 tending to cause the upper auxiliary piston 117 to rise in the cylinder 112. r

When the main piston 98 has been forced up to the point where it uncovers the relief port 105 any further oil which is pumped into the cylinder will escape into the passage 106 through the passage 107 back to the crank case When the piston 98 is in the position described the operating arm 38 will have been permitted under .the influence of the springs 33 to be raised to such a position that the suction valves 27 are free to function in their usual manner.

" The piston98 with its spring 104 performs a dual function. The spring '104 tends primarily to lower the rod 100 and pull down the unloader lever 38 for opening the inlet valves of the compressor. 'T he primary purpose of the piston 98 is to overcome the spring 104, lift the rod and thereby cause loading of the compressor.

But by means of the overrun port in the wall of the cylinder, the spring104 and piston 98 perform the important function of a bypass or loaded relief "alve, which serves as a pressure maintaining valve, for retaining sufiicient pressure in the hydraulic system to insure that first the switch will be kept closed and second that the unloader will be kept inactive so long as the P139118, termined speed is maintained and the feeding ofoil' otherwise satisfactorily maintained. Thus the leakage port 68 insures that the desired hydraulic pressure will not be built up until the predetermined speed of the compressor is attained and the piston 98 and port 105 insure that no more than a desired operating pressure will be retained for all higher speeds. v

.The leakage port 68 is. in constant communication with the unloader cylinder and tends to deplete the pressure, but during I normal compressor operation the pump 47 'maintains the pressure-of-oil in the hydrau- A termined by strokes of the pump the unloading mechanism has been operated to put the suction valves in operating position and the compressor is running the piston 98"remains at a distance above the upper auxiliary piston 117 in the position.dethe port 105. The auxilia'ry piston 117 has been raised by its. spring 122 into the position shown in this figure and the' space between the upper auxiliary piston 117 and the lower auxiliary piston 118 isfilled with the liquid under pressure.

Raising the operating "arm 38 of the unloading mechanism serves to open the valve 39 which is connected in the cooling water system. An upon the unloading shaft 34 and carries at its outer end 126 an adjustable spring plunger 127 which bears against the valve operating rod 128 provided-at its outer end with a piston member 129. The piston member 129 bears against a diaphragm 130 which closes off one side of the valve body 131. A

valve member 132 is guided to cover and uncover the ports 133 when the operating rod 128 is moved in or out. The valve body 131 has an outlet port communicating with the pipe '134 that leads to the cooling jacket of the cylinders. It can be seen that as'the operating arm 38 of the unloading mechanism is raised by the springs 33 the valve member 132'will be released from the seat at the port 133 and the pressure of the water will open the valve and permit the cooling water to flow through the cylinders. The valve member 39 permits cooling water to enter the jacket as long as the unloading device permits the valve 27 to function.

Assume that the operation of the compressor has raised the air pressure in the main tank-43 to the desired point and that the air governor 41 operates as will be described later to stop the operation of the compressor.

When the air pressure in the main tank '43 reaches the desired point air under pressure will be admitted from the auxiliary reservoir 42 to the pipe 90 from whence it flows into the chamber 89 raising the 'diaphragm 87 thereby opening the 'valvef83. When the valve 83 is opened the liquid underv pressure escapesthrough the port. 84 to the discharge pipef93 and back to the crank case. This release of pressure is grad-- ual and the first consequence of the same is that the spring 104 begins to force the piston 98 of the unloading cylinder downward.

The piston 98 will oscillate slightly with the I "through the port 84 the stem 124 of the piston 98 will finally strike the top of the aux-- iliary piston 117 thus closing OK the port 123 in the top of that piston, trapping the oil between the upper piston 117 and the lower piston 118 and as the pressure is further-"reduced the spring" 104 will exert its adjustable arm 125 is mounted 47 but as the oil escapespressure against the upper piston 117 and the piston 117 in turn transmits the pres sure to the lower piston 118 through the medium of the trapped oil between these parts thus forcing the lower piston 118 downward and o ening the valve 111 thereby permitting t e oil within the cylinder 96 to escape rapidly through the orts 114 and through the port 110.. As t e lower piston'118 is thrust downward it uncovers the intermediate ports 116 and permits the oil toescape from between the two pistons and finally permits the and the. parts to assume in Fig.9.

\Now, it will be apparent that the organization comprising valve 1:11 and its connected piston 118, to ether with the cooperating cylinders; cylin er ports and t he intermediate piston 117, constitutes a qiiick rethe position shown and complete evacuation of pressure in the v'alve111 to close system so that unloading may be positively secured and opening of the resistance control switch andthe main switch be invariably accomplished when the hydraulic. pressure declines to a predetermined minimum. It is to .be particularly noted that this organization of elements does not operate the same upon a rising or increasing pressure. Then no release of pressure should occur, and none does occur. The motor 2 during normal operation maintains a substantially constant speed so that very little variation inpressure in the hydraulic system occurs. Such minor variations as do occur are absorbed by the lost motion of the piston 98 and port with respect to each other. That is to say for slightly higher speeds the port 105 is opened more and for lower speeds it is further closed. ,Hence the.quick release device may be made highly sensitive to trip out sharply and promptly upon the decline of pressure. in the hydraulic system below that corresponding to the required speed.

After the unloading mechanism has thus been operated to unload the valves 27 the pressure of the oil in the hydraulic main and connected parts. will drop to such a' point that the spring 76 of the switch oper ating cylinder 73 will overcome the oil pressure and the starting resistance short circuiting switch will be opened. As the piston rod 7 5 drops downward it trips out the main switch17 by means of a mechanical release as will-be described later.

It will be noted that due to the proportions of the spring strength of the cylinders 73 and 96 the starting resistance will mechanism has been set forth sufiticiently so that certain advantages of this type of control and of the particular combination of elements is now apparent. .If through an accidentalleak in any part of the oil system or a gradual using up of the oil in the compressor it should occur that the oil should drop down to the danger level represented by the line 59, the compressor could ,/not be loaded. This is apparent because the pump .would be unable to draw oil after the level of the oil fell below the suction intake 60. There might be sufficient oilto close the resistance short circuiting switch 26 but in the event of any shortage of oil whatsoever the compressor will not be loaded. When the compressor reaches full or normal speed it will lower the level of the oil further by splashing and by carrying more on the gears and soon draws the level so low that the oil pump draws air. This immediately results in a drop pressure in the hydraulic main. The first consequence of this reduction in pressure in the'hydraulic main is that the spring 104 begins to force the piston 98 of the unloading cylinder downward causing the piston 98 to strike the auxiliary piston 117 and, as hereinabove described,

the port 110. Before the valvev 111 has been again seated sufiicient oil has escaped from the hydraulic main to effect the opening of the main switch. However the machinery will not be running dry when the oil has reached the danger level as there is still ample to protect the machinery against damage. The operator or .attendant is warned of the danger by opening of the main switch and refusal of the compressor to start automatically. Inspection of the gage-glass 54 will reveal the cause of the difliculty. If any rupture of the oil conveying pipe or of the oil containing chamber should occur or in the event that the machine is notjrunning at proper speed the same condition of control will prevail. If the loss of oil is sufiicient to rob the switch operating cylinder of oil the main switch will automatically open within a very short time after it is closed by leakage of the air from the auxiliary reservoir as will be described later. The hydraulic system and connected partsis primarily a protecting system. ,If the motor does not come up-'to speed the pump will fail to accumulate pressure may' be nicely predetermined by' adjustment of the size of the orifice. Any

condition electrical or mechanical which would prevent the motor from properly force the valve 111 off of its seat and open- The starting re- Automatic air governor.

The automatic air governor 41 is of a tpe heretofore known and will not be descri ed in detail except where the same is necessary to set out thefunction of the same in the present system. Any other form of governor which is capable of closing the main. switch when the pressure in the main reser-. voir 43 has. dropped down to a pre-deter mined cut-in-pressure and which would operate to open the valve 83 when the pressure in the main reservoir had been raised to a certain pre-determii ed cut-out pressure, might be used. The governor 41 comprises a main body portion having an inlet port 136 connected by the pipe 44 to the main reservoir 43. The main body is pro-' vided with two outlet ports, one of which 137 is connected to the auxiliary reservoiri. 42, and the other 138 is connected by means of a pipe 139 to a valve operating cylinder 140 mounted in the cylinder head 1'41 of the main switch operating cylinder 142. The main body of the governor 135 has an open central passage 143 which is provided at its upper ,end with a cylinder bore 144 within which is fitted a sliding piston 145. At the other end of the central borethere is foi'med a cylinder bore 146 within which is slidably mounted a piston 147, the piston 147 being of a smaller diameter than the piston 145. These two pistons and'147 are connected together by a stem or rod 148 which has a pair of collars'149 between which is mounted a slide. valve 150 which valve is pressed against a suitable valve surface 151 by means of a spring 152. The space 143 between the pistons 145 and 147 communicates through the port 136 with the pipe 44 connected to the main reservoir. The space 152 "between the piston 145 and the cylinder head 153 communicates by Way of a port 154 with the cut-out valve 155; this valve 155 normally closes against its spring 157. The valve 155 is provided with means for opening the same, this means consisting of a plunger rod 158 connected to a piston 159 and guided in a suitable nut 160. A spring 161 the tension of which may be adjusted by the nut/ presses thepiston 159 against a diaphragm 162 tending to hold the plunger rod 158 away from the valve 155 thus allowing the same to close. Upon the opposite side of the diaphragm 162 is provided a chamber 163 to which compressed air may be admitted through the port 165 and passage 166. A suitable supporting block 167 holds {he diaphragm provided with adjustable b 162 in place and prevents damage to the same from tension of the spring 161.

The space between the piston-147 and the cylinder head 168 is connected through a valve port 169 and a passageway 170 with the valve port 171 which is controlled by the cut-in valve 17 2. The piston 147 has a boss or projection 173 which is adapted tocover the valve port169 and to close oif the same when the pistons 145 and 147 are moved to the lowermost position as is indicated in a suitable pressure is created in the chamber 179. The-strength of the spring 180 is means of the nut 182.

The cham er 179 is always in communication with the pressure in the main reservoir 43 by way of the passage 183 which branches ofl from the passage 136. The passage 137 communicates with the interior of the cylinder space 143 by means of the two. valve ports 184 and 185. These two ports are not essential and could in this case be combined into one. The operation of the air governor 41 will now be described.

Operation of the air go'uemor.

It is to be noted that the tension of the springs 161 and 180 are so proportioned with respect to their diaphragms that the same air pressure operating against these springs fore it would the sprin Were the pressure to rop the spring 161 would first move its plunger inward before the spring 180 would move its plunger inward. I

The plunger 176 through its diaphragm 177 is constantly in communication with the pressure in the main reservoir 43 and when the pressurev drops below a certain value at which it is desired to have the compressor start to replenish the supply of compressed air in the main reservoir 43 the spring 180. will move the plunger outward withdrawing the rod 178 from the valve 172 thus allowing the port 171 to be uncovered and .permitting the piston 147 to the air which is l in outside-of be exhausted. he cut-out valve is closed at this time due to the fact that the pressure in the main reservoir is not suflicient at this time to overcome the spring 161. The valve 155 having been The valve 172 which is termed the "cut-,

would overcome the spring 180 be-x 161 and vice versa.

closed for some time the pressure in the central space 143 and in the upper cylinder space 152 has been udmd... Consequently when the cut-inva Va 17 2 is opned by the ressure reaching the predetermined value, t e pistons 145 and 147-will be moved downward into the osition shown 5.- In this positionthe port 169 is closed 011? to prevent leakage to the passageway 17 0 and the valve body 150 is shifted to such a position where it connects the passageways 184 and 185 with the passage 138 and cuts off communication between pasageways 184 and 185 with the central space 143. As a consequence the compressed air which is trapped in the auxiliary reservoir 42 and connected pipes flows through the port 137, passageways 184 and'185, passage 138 and pipe 139 into the valve chamber 140 of the main switch operating cylinder 142. This causes the main switch 17 to be closed in a in Fig.

manner, which will be described later, thereby starting the motor. held closed by the air pressure back of it and as the pump 47 begins to operate it begins to move the plunger 77 for the starting resistance sholt-circuiting switch 26 to close. Movement of the plunger 77 upward re leases a ,mechanical catch which will hold the main switch in position as will be described later. After the starting resistance is cut out the compressor is loaded as pie- The main switch 1s viously described and compressed air is delivered to the main reservoir 43. The pressure is thus raised in the main reservoir 43 until it reaches the desired maximum pressure at, which the compressor is to be stopped. 'When this pressure is reached air passing through the port 136, through the central space 143, through the port 165, passage 166 and into the chamber 163, raises the plunger 159 thereby moving the valve 155, which is termed the cut-out valve, oil of its seat 156, permitting the escape of pressure from the cylinder space 152 above the piston 145.

As the air pressure increased it operated upon the piston 17.6 to close the valve 172 before the valve 155 was opened. This, as previously explained is due to the diiferent spring strength for the two valves. As' soon as the cut-in valve 17 2 had previousl closed, the air pre$ure had equalized itself upon both sides of the piston 147 so that when the cut-out valve 155 was opened and\ released the pressure'in the space 152 the pistons 145 and 147 moved upward to the uppermost communication between these passages and the central chamber 143 so that air at the then high. pressure may pass from the main reservoir 43'by way of the pipe 44 and port- 136 to the central chamber 143 and through opening *of the starting resistance'switch 26' which in turn trips out the main switch as will be described below.

From the above it is apparent that the governor operates at a predetermined minimum pressure in the tank 43 to close the main switch, bring the motor to speed, short circuit the starting resistance. and thereafter load the compressor and permit operationbt the same until a predetermined. maximum pressure is reached in the main reservoir. Then this predetermined maximum pressure is reached the governor operates to open the hydraulic main, thereby causing unloading of'the compressor. opening of the start: ing resistance switch 26 and tripping out of the main switch to stop the motor.

Circuit cmmmfions.

ling the. same. In this connection it is to b6110td that I have illustrated a threephase power circuit but it is apparent that other types of power may be employed if found. desirable. The incoming line wires 187, 188 and 189 are joined by separable connectors 190 of any preferred type to the wires-191, 192 and 193 respectively of which the wires 191 and 192 are connected to suitable terminals 194 and 195 which are suit ably insulated from the switch-board base 25. The terminals 194 and 195 are connected to the relatively'stationary contacts 196 and 197 whielrare mounted upon the front *of 'the switch-board. The relatively .sta lionary contacts 196 and 197 comprise a pivoted arm 198 swinging about a shaft 199 and pressed dowuby a spring Upon the outer end of the. arm is mounted an are receiving contact 200 for making the initial and final contact with the corresponding member of therelatively movableterminals. The conducting or actual switching contact 201 is mounted back of the are receiving contact 290 and is adapted to make permanent contact during the time that the switch is closed and to carry the necessary current. These contacts 200 and 201 are connected through a suitable flexible conductor or strap 202 to the terminals 194 or 195 mounted upon the rear of the board 25.

The one main line wire 189 is' connected directly to the motor through the lead 193 as it is unnecessary to lead this line Wire through the main switch. The other two primary leads 204 and 205 are connected through suitable connectors 190 to the wires 206 and 207 respectively, which are joined to suitable terminals 209 and 208 upon apair of lugs 210 and 211 forming a part of the switch operating cylinder 142, the terminals being suitably insulated from the frame of the machine.

The switch operating cylinder 142 is provided with a spring containing housing 212 and a pair of stationary wiping contacts 214 and 215 lie along the side of this housing with plates of insulation 216 and 217 interposed. The operating cylinder 142 has a plunger rod at 218 which bears at its upper end a contact bearing frame 219 which supports the relatively movable contacts 220 and 221. These contacts are'constructed in substantially the; same manner as the. contacts 196 and 197 except that the same are not mounted to be yielding. The transverse .frame 219 carries a plurality of insulating barriers 222, 223, 224 and 225 which form a,

pair of arc chambers 226 and 227 for the .contact pairs 196 and 220 and 197 and 221 respectively. The barriers 222 to 225 are spaced apart suitable insulating collars through which clamping bolts are passed. The movable contacts 220and 221are connected by means of movable wipers 228 and 229 to the stationary wipers 214 and 215. It

can now be seen that when the contacts 220 and 221 are brought against the contacts 196 I and 1.97, the line wires 187, 188 and 189 will be connected directly to the primary leads 13 of the motor 2.

The secondary leads 18 are connected to the three wires 230, 231 and 232. The wire 230 runs along the back of the board 25 and is connected to a suitable terminal 233 which is mounted on an insulated support and provided at its upper end with a flexible connection 234 which connects it electrically to the upper end of the compressible resistance 22. The resistances 22, 23 and 24 are constructed of suitable pieces of carbon formed preferably in the shape otdisks lying in a suitable tube in a manner well known in the art.

The conductor 231 is connected to a metallie connecting member 235 shown in dotted lines in Fig. 13. This connecting member 235 has its ends 236 and 237 projecting forward and resting upon suitable lugs formed upon the operating cylinder 73 for the starting resistance switch opera-ting cylinder. These end terminals 236 and 237 are connected to stationary wiping contact plates conductor 261. The compressible resistance I platesand are connected at their upper ends to the movable contact members 78 and 79 respectively, these contact' members being supported u :-on the cross frame member 244. The cross rame member supports a plurality of barrier members 245, 246, 2 7 and 248 which form a pair of spark chambers for the contact pairs 78, 80 and 79, 81, respectively. v

The contact member 235 is connected by a wire 249 to a terminal 250 upon the front of the board near the switch 26 and back of the same. This terminal is in turn connect ed by a strip 251 on the front of the board to a bolt which" connects it to a terminal 252 on the rear of the board 25. The terminal 252 is connected by a flexible conductor 253 to the terminal 254 upon the upper end of the compressible resistance member 24.

The conductor 232 is connected to a terminal 255 on the back of the board 25 which terminal is in turn connected by a flexible connector 256 to the terminal 257 of the compressible resistance 23. The lower ends of the compressible resistances terminate in conducting members 258, 259 and 2 which I are joined'together by a common flexible members 22 and 23 are supported at their lower ends upona lever 262 that is pivoted at its center to the frame member 25. The lower end of the compressible resistance member 24 is supported upon an arm or bracket 263 which is held stationary upon the back of the board 25. The upper end of. the resistance member 22 is provided with an insulated stud 264 which engages the end of a lever 265 pivoted on a pin 266 at the top of the board 25. The upper end of the compressible resistance member 23 is also provided with a compression stud 267 which engages one end of the lever 268 which'is pivoted at its center to a bracket member 269 mounted near the upper end of the board 25. The other end of the lever 268 engages the compression stud 270 on the upper end of the compressible resistance member 24..

It can now be seen that any pressure exerted by the lever 265 upon the upper end of the compressible resistance 22 is transmitted substantially undiminished to the other resistance members so that they are all compresd substantially equally. w

The lever 265 is adapted to be moved to compress-the starting resistances 22, 23 and M by upward movement of the piston rod previous to closing the switch 26. The

1. rod 75 carries at its upper end a collar 275 upon which rests an insulating collar 276 carrying a guiding sleeve 277 for guiding a spring 278. The lower end of the spring rests upon the collar 27 6 and the upper end of the spring engages a collar 279 which is adapted to engage the longer arm of the opcrating lever 265 'for compressing the resistances. A hollow cylindrical member 280 is connected to the collar 279 and is adapted to telescope within the sleeve 277 for guiding It can now be seen that asthe cylinder 73 is dumped full of oil and raised the piston rod 75 pressure will be transmitted through the spring 278 and arm 265 through the starting resistances 22, 23 and 24 and the resistance of these members decreased so that a greater flow of current may occur for speeding up the motor 2. When the piston 75 has moved to the top of the stroke the switch 26 will be closed and the resistances short circuited.

.J I shall now describe the structure and operation of the main switch operating cylinder 142 and connected parts.

ZIIai-n switchloperating cylinder matz'c blow-out.

' The cylinder head 141 of the main switch operatingcylinder 142 is provided with a and pneuboss 283 which has formed therein a Plurality of valve ports and passages later to be 284 comprises a cylinder having the cylinder-lining 285 within which slides the cylindrical portion 286 of a valve member 287 which is provided at its upper end with an enlarged shoulder or flange 288Ybearing a yielding seat 289 which is adapted to engage the rim of the passage member 290 which 1 ,The valve member 287 has a central bleed ing port 292 and this port permits the pressure within the chamber 140 and the pipe 139 to escape after the cylinder has been 0perated to close the main switch 17.

y The cylindrical portion. 286 of the valve member-287 is provided with a. valve port 293 which when the valve member is forced to its lowermost position as shown in' Fig. 11 is entirely covered by the cylindrical liner 285. A spring 294 is employed to hold the valve "away from its seat 290 and thus permits the passage 291 to be put in communication with the interior ofthe cylinder by way of the passage 295. The cylinder 142 is .described which boss is covered by the recessed cap member 284. This cap member provided witha closely fitting piston 296,

e which may be of any desired construction which is connected to the piston rod 218. The upper end of the cylinder is provided with a housing 212 for a spring 297 (see Fig. .4) which spring extends down to a point within the cylinder 142 where it rests upon the flange 298 of a spring housing sleeve 299. Within the housing 299 a spring 300 of less strength than the spring 297 is housed. The upper. end of the spring 300 bears against an internal flange 301 of the sleeve 299 and 'thelower end of the spring rests against the top of the piston 296. v a

It will now be seen that when the governor admits air under pressure to the pipe 139, the valve member 287 is immediately raised and closes off the valve port of the member 2 90. At the same time the valve port 293 which is formed in the side of the valve member 287 is uncovered so that the air under pressure passes through the passage 295 into. the interior of the cylinder 142 overcoming-the spring 300 then engaging the lower end of the spring housing 299 and forcing the same upward against the tension of the spring 297 to complete its stroke.

The completion of the stroke closes the main switch 17 by bringing the contacts 220 and 221 against the relatively stationary contacts 196 and 197. i

For the initial closing of the main switch 17 before any pressure hasbeen created in the main reservoir 43 I provide a lever 303 which has a socket 304 at its outer end for receiving a suitable handle 305. This lever is pivoted to the base-board 25 at its rear end by means of the bolt 306 and is provided with a roller 307 which is adapted to engage a bracket 308 formed upon the rear of the cross-frame 219. The bracket 308 is provided with a. shoulder piece 309 that is' adapted to engage a suitable catch or detent 310 mounted on the upper arm ofa bellcrank men'iber 311 which has a horizontalarm 312 which extends back of the piston rod-75 of the startin resistance switch 26. V 1 h lhe transverse frame member 244 which is 'fastened on the piston rod 75 has a projecting finger 313 (see Fig. 12) which'is adapted to strike the arm 312 and push it down against its spring 314 thereby tripping out the main switch. Thus when the starting resistance switch 26 opens and releases the compression of the resistances 22, 23 and 24 the finger 313 strikes the horizontal arm 312 and releases the movable members of the main switch 17 which main switch member is then moved downward under the combined influence of the two springs 297 and 300, Since the pressure in the chamber 140 and in the cylinder 142 has leaked away through the bleeder port 292 the valve member 287 will have been moved downward into the po-' pipe 326 to the hydraulic main 66.

sition shown in Fig. 11 because of the pres-- that when the, switch is tripped out and starts to open the air in being expelled from the cylinder 142 is projected into the are chambers 227 and 226 in suitable position to blow out the arc which may be drawn be-' tween the movable and stationary contacts.

I shall now describe a feature of electrical protection for the motor.

Over-load protective device for the motor able position back of the main switch 17 so In Fig. 14 I have.shown a wiring dia-" gram of the motor and connected parts which varies from the connections shown in Figs. 4 and 13 in changing the connection The winding 318 is connected to the short, circuit connection 78 and 79 of the starting resistance switch 26. This winding forms a solenoid supported upon a suitable frame 320 of magnetic material and having a plunger 321 projecting into the winding 318. The upper end otthe plunger 321 is connected to a valve member 322 which closes off an exhaust port 323 to normally shut off the oil chamber 324 which is formed on the upper end of the solenoid frame 320 from the overflow pipe 325 which connects with the crank case. The. chamber 324 is connected by a Thus when the main switch 17 is closed and the motor brought up to speed by closing oi' the $01 the load becomes too severe the solenoid will open the valve 322 and thus prevent damage to the motor. The load at which the solenoid trips out the valve maybe adjusted by means of a spring 327 the tension of which is controlled by a set screw 328.

The relay *will not be influenced by starting current as it is not in circuit until the switch 26 is closed. Hence even if a large starting current is drawn no operation of the relay results, but after the switch 26 is closed the relay will releasethe pressure and so until the desired maximum pressure was cause opening of the main switch if more reached. While the main reservoir is being than full load current is drawn. filled Wltl compressed air the port 165 is uncovere and when the ressure reaches a Geneml opemfwnof he w certain. predetermined poiiit where the co-m- 70 1 shall now describe in general the oper- Presser i t b t p d th air acti g upo ation of the devlcc. the diaphragm. 162 and piston 159 thrusts h Order to Start compressor when the rod 158 upward and opens the cut-out there is no pressure in the tank 13 the hanal 155 Th i t t t r 145, 147 i d le 305 is inserted in the socket 304 of the th promptly moved to the upper position 7 lever 303 and the main switch is manually as Shown i Fi 8 th b uncovering the closed and held in that position while the valve ports 184, 135 d mitti g e otor s st te AS S0011 as the 11101101 9- pressed air at full'pressure to enter the aux.- g S tllrhlllg h p Shaft W111 iliary reservoir 42 and from thereto enter also be turned and the pump 47 willbe operthe pipe 90 and the chamber 89 b l th .80 'ated to create a press re in the hy r diaphragm 87. The pressure of the air is main 66. The swltch-must be. held closed such as to vovercome the spring 91 and open as he latch memb r 1 t ipp 0111? the valve 83 permittingthe oil which enters by the finger 313 striking, the arm 312. A by the passageway 72 and some of the oil 011 is pumped into the hydraulic main it i th li d 73 t escape b i t th 85 exerts a pressure against the piston 77' in crank h b n The spring {04 immedithe cylinder 7 3,'the valve 83 being closed at t l causes th l r 98 a d nnectd this time- This raise? h I rod 50 parts to drop down between strokes of the that the finger 313 dlsengages t e h-. oil pum 47 because of escape of liquid from I tal arm 312 of the latch member 310 and th hy a li system until the stem 124 \3 311 and permits it to engage the shoulder which is below the piston 98 strikes the top 309 and hold the maln switch 17 ma closed f th upper iliar piston 117 closing ofi position. Asthe rotatlon of the motor 0011- the ort 123 and forcing this piston 117 tinues the hydraulic main and connected d w d, The oil which is trapped bc- 30 Parts will be P p fun of 0.11, the Piston tween these. pistons 117 and 118 transmits 77 being sl wly r i n il the switch 26 the pressure toithe lower piston which is is GIOSBd- The mpr s Startmg G moved downward to open the valve 111. ances 22, 23 and 24 are compressed by the Op'enin' of this valve quickly permits escape compression which is placed pon h pr g' of oil f rom the cylinder 96 and allows the 35 278 as the piston moves upward. When piston 98 to descend to its lowermost posi- 100 sufiicient O l has be n p mpe n the y1 tion, as is shown in Fig... 9 where it rests inder 73 the switch 26 will be closed and the against the top-of the auxiliary cylinder 112. resistance cut out of the secondary of the By downward movement-of the piston 98 motor which will then'begin to operate at the stem 100 is drawn down thereby moving 40 full speed. As previously explained the the operatinglever 38 of the unloader mechspring76 of the piston 73 is of less Streng h anism pushing the suction valves 27 off of than the spring 104: of the piston 98.: Contheir seats and holding the same in that posequently a further increase in pressure in sition and closing the water valve 39 for the hydraulic system must be accumulated cooling the cylinders.

45 before the Strength of the spring 104 can The cont nued leakage of-oil through the y be overcome. This will occur as clearly valve 83 a (1 through the valve 111 permits s w after. he motor reaches full speed the piston 7 to descend and open theswitch and as a consequence the piston 98 will be 26 and thereafter releases the pressure upon raised permitting the operating arm 38 of the compressible starting resistances 22, 23

5 the unloader to rise and release the suction and 24 to increase the resistance in the 115 valves 27. At the same time the valve 39 secondary circuit of the motor. As the which controls the cooling water is alplunger 75 moves downward the finger 313 lowed to open and the compressor begins engages the arm 312 thereby tripping out to operate, As the compressor begins to the main switch 17 and permitting it to open 55 operate it creates a-pressure in the main .under the action of the springs 297 and 300. tank 43 which being transmitted to the The initial movement of. the piston 296 in *pneumatic, governor 41 closes the cut-in the cylinder 142 is rapid because of the Valve 172. 1 relatively greater strength of the spring 7 The piston structure 145,147,if it was not 297 and as a consequence the air which is 60 already in the lowermost'position was moved trapped in the cylinder is discharged to the lowermost position, as is shown in through the passageway 295 through the- Fig. '5 as'soon as any pressure was created passage member 290 into the passageways in the 'main reservoir. This is because the 291 and 315 to the blowoutnozzles 316 and cut-in valve 172 was then opened and the 317 which extinguishwpy are that may be cut-out valve 155 wasclosed and remained drawn between the contacts of the main switch 17 thus efl'cctively opening the circuit. The spring 300 brings the piston'296 =down gently against the cylinder head 141.

The main reservoir 43 is now full and the motor has been stopped.

It will be-noted that rovision has been made for preventing the idle running of the compressor if the body-of lubricating oil in the/crank case has dropped below the proper level, either by leakage or otherwise, in that the holdingin of the main switch is dependent upon the catch 310 and it this catch is not released by rising of the cut-out switch 26 the air pressure which raised the plunger 296 of the main switch will soon leak away through the escapernent or bleeder port 292 until the valve body 287 drops down and the switch descends and opens the circuit. That is to say, assume that the valve 150 of the governor 41 has been moved to the position shown in Fig. 5 whereby the auxiliary reservoir 42 is connected to the pipe 139 and to the cylinder 142, the piston 296 will be raised thereby closing the main switch 17 and starting 'the motor. The amount of air delivered bv the auxiliary reservoir 42 is suflicient to hold the main switch closed for a short time which is under normal circumstances. amply suiticient for, the pump 47 to fill the hydraulic system with oil and to begin raising the plunger 77 for the cut-out switch 26 If however due tosome fault of the electrical apparatus the motor does not start or if due.

to friction it does not properly speed up the pressure will not be built up in the hydraulic system to raise the plunger 77 theair in the main switch cylinder 142 will gradually escape until the valve 287 drops down and permits the air in the cylinder to exhaust through the blow-out passages and nozzles thereby causing the switch to open and shut down the motor.

Such cutting out of the motor and stopping of the compressor occurs if a phase is open as by blowing of a fuse and drop- .ping off in speed or if excessive friction is created or if the voltage drops too low or when the coil is'used up or leaks until it is down to about the danger level.

It is to be noted thatthe cut-out valve 155 closed as soon as the piston structure 145, 147 and the valve 150 were shifted to the uppermost. position because of the connection of the port 165 with. the passageway 138 which communicates with the pipe 139 .and the chamber 140 in the main switch "cylinder head. The small amount of air WlliGhjVilS contained in the chamber 163 back of the operating piston of the cut-out valve is thus exhausted permitting the valve to close immediately.

' and 155 are closed.

lVhile the reservoir is full both valves 172 As th'eair is used from the reservoir 43 and the pressure therein dropped to a predetermined minimum where the compressor is again to be started the spring 180 overcoming the air pressure in' the chamber 179 opens the cut-in valve 172 permitting the exhaust of air from belowthe smaller piston 147 thereby causing the piston structure to move downward and con'-' nect the passage 138 with the ports 184, 185 that connect with the auxiliary reservoir 42 which is-full of air at main tank pressure. As soon as the valve is thus shifted theair from the auxiliary reservoir 42 flows through the pipe 139 into the chamber 140 of the valve 287 causing the valve to rise and close off the port 290 thereby permitting the air to pass through the port 293 and passageway 295 into the cylinder 142 to raise the piston and close the main switch 17..

Th operation from there on is the same as previously described.

I shall now describe the structure and operation of the modification 16 and 17.

The mechanism of the governor350 is mounted upon a base portion 351 and is inclosed in a suitable cover 352. The diaphragm plate or piston 353 is provided with a series of stems 354 and 355 which pass up through the base and are in direct communication with the springs 356 and 357 by shown in Figs.

means of a collar 358. uThe. collar 358- is 3 provided at its upper end with a guiding sleeve 359. The lower ends of the springs 356 and 357 rest upon the collar 358 and the upper ends of the springs engage a collar 360. A suitable shaft disposed within the guiding. sleeve 359 is provided at its lower end with a stem 362'which is threaded through the base 351. forming a suitable stop for limiting the upward travel of the diaphragm plate 353. The upper end of the shaft 'is provided'with a reduced threaded portion 363 which passes through the col' lar 360 and is threaded into an adjusting nut 364. The-cutting-out pressure at which the governor has been set to operate may be changed by increasing or decreasing the tension on the springs 356 and 357 i by means of the adjusting nut 364.

The diaphragm plate or piston 353 rests upon a flexible diaphragm 365.- The diaphragm is held in place by a recessed piston head 366 the recess or chamber 367 of which is at all times in direct communication with the main reservoir 43 by means of the pipe line 368.

A movable contact carrier is pivoted by means of a pin 370 to a pan of togglearms or links 371 and 372. The links 371 and 372 are connected to the collar 358 by a pin 374. A pair of suitable springs 375 and 376 are secured under tension to the pins 37 3 and 377 (as shown in 17) to insure a quick and positive toggle inovement of the contact 378 from one extreme to another. 

